Sharla Rausch, director of the DHS's human factors division, says the agency is already seeing positive results. In a controlled lab setting, she says, accuracy rates are in the range of 78 to 81%. The tests are still producing too many false positives, however. "In an operational setting, we need to be at a higher level than that," Rausch says, and she's confident that results will improve. At this point, though, it's still unclear how well the systems will work in real-world settings...

By combining the results for all of these modalities, the DHS hopes to improve the overall predictive accuracy rate beyond what the polygraph -- or any other means of testing an individual indicator -- can deliver.

That's not a very high bar. The validity of polygraphs has long been questioned by scientists, and despite decades of research and refinements, the results of lie-detector tests remain inadmissible in court. While the U.S. Department of Defense's Defense Academy for Credibility Assessment (DACA; formerly the Polygraph Institute) puts median accuracy percentage for polygraphs in the mid-80s when properly administered, others say that number is closer to 50% in the real world and that the results depend heavily on the skills of the examiner.

Schneier goes even further. He says lie detectors rely on "fake technology" that works only in the movies. They remain on the scene, he says, because people want them to work...

The TSA's passenger screening technology hasn't changed since the magnetometer, a metal detector, was introduced in 1973, but it's working on other technologies...

"We are not going to catch any terrorists, but a lot of innocent people, especially racial and ethnic minorities, are going to be trapped in a web of suspicion," says Barry Steinhardt, director of the Technology and Liberty Project at the American Civil Liberties Union in Washington.

But Steinhardt isn't really worried. He says Project Hostile Intent is just the latest in a long string of expensive and failed initiatives at the DHS and the TSA. "I've done hundreds of interviews about these [airline-passenger screening] schemes," he says. "They never work." Steinhardt adds that "hundreds of billions" of dollars have been wasted on such initiatives since 9/11. "Show me it works before [we] debate the civil liberties consequences," he says.

Given the DHS record on cybersecurity and other information technology issues--and the record of the US government in general--perhaps Steinhardt is right.